When you create a new report, it will ask for the data source.
Select SQL query as the data source. When you created the query, you must have specified the datasource, either by ODBC connection OR by sselecting the tables.
Now when you attach the query in the report designr, you will get the data source also.
Have you tried this ? (i.e. Selecting the option of SQL query as the source for data to the report ?)